Vehicle checks and on-site patrols of Army, Navy and Air Force sites in Victoria won't be done by Wilson security guards as they take protected industrial action over a pay dispute.
From 6am Thursday, guards will refuse to do duties on Defence Department sites such as processing visitors, bag and vehicle checks and site patrols, according to the guards' union, United Voice.
The union says the guards have been in negotiations with Wilson for more than a year, have not received a pay rise in nearly two years and that the company wants to put employees on a minimum award and cut penalties.
"We all rely on Defence guards to keep our men and women in uniform safe and they take that responsibility very seriously," United Voice Victoria Secretary Jess Walsh said.
"Wilson guards have done everything they can to make their voices heard and protect their hard-fought professional standards, They have negotiated in good faith, signed petitions and rallied but Wilson has fought them at every step."
Sites affected include the Australian Geospatial Intelligence Organisation site near Bendigo, Simpson Barracks in Watsonia and the HMAS Cerberus Naval Base on the Mornington Peninsula.
The union says 97 per cent of guards who voted on the action supported the move and it could escalate to walking off the job if Wilson retaliates.
If an incident occurs, guards will resume normal duties.
About 200 highly-trained guards man entry and exit points at the sites across Victoria, checking access cards, verifying identification, maintaining entry-exit records, monitor surveillance and patrol grounds.
Wilson Security and Defence have been contacted for comment.